Enormous amounts of ash are produced in the generation of electricity using black coal-fired burners. Fly ash is generally captured from the chimneys of power generation facilities, whereas bottom ash, as the name suggests, is removed from the bottom of the furnace. In the past, fly ash was generally released into the atmosphere, but pollution control equipment permits the capture of fly ash, preventing its entrance into the atmosphere and reducing its pollutive effects.
One component of fly ash is cenospheres, which are spherical inorganic hollow microparticles comprising the lightest component of fly ash. Cenospheres typically comprise approximately 1%-2% of fly ash and can be recovered or “harvested” from fly ash.
Given the large amounts of fly ash that are generated, the continued retention and storage of fly ash is problematic. In an attempt to address the accumulation of fly ash, several processing methods exist to utilize or dispose of fly ash in a satisfactory manner. Methods along these lines involve the formation of aggregates and other materials, whereby a polymeric binder or a cement is mixed with the fly ash. However, these methods suffer from several disadvantages, including but not limited to, that relatively small proportions of fly ash can be used, substantial heating is required, or the cost of the binders/cement results in an expensive product.
The recycling of fly ash has become an increasing concern in recent years due to increasing landfill costs and current interest in sustainable development. In 2005, U.S. coal-fired power plants reported producing 71.1 million tons of fly ash, of which 29.1 million tons was reused in various applications. If the nearly 42 million tons of unused fly ash had been recycled, it would have reduced the need for approximately 33,900,000 m3 of landfill space. In addition, recycling fly ash provides other environmental benefits, such as reducing the demand for virgin materials that would need quarrying and substituting for materials that may be energy-intensive to create (e.g., Portland cement).
There is currently a great demand for strong and lightweight materials that are easily and economically manufactured. Such materials have long been sought by the construction and automotive industries to increase the strength, durability, and resilience of structures while reducing the weight of the structure. In the context of the construction industry, such materials can make buildings more resistant to natural disasters (e.g., earthquakes), whereas strong, lightweight materials can reduce the energy consumption of an automobile. In addition, there is a demand for porous materials as they can act as sound or thermal insulators and as shock absorbers. However, presently available materials that meet these criteria, such as metallic foams, are very expensive. Furthermore, there is a great demand for environmentally-friendly “green” materials.
Accordingly, there is a need for strong and lightweight materials that are environmentally-friendly and can be manufactured economically. It is to the provision of such materials that the various embodiments of the present invention are directed.